Field of the Invention
The present invention relates to original reading apparatuses for reading images of originals.
Description of the Related Art
Original reading apparatuses such as copy machines, facsimiles, image scanners, and so on typically read an image of an original by illuminating the original, which has been placed on a platen glass. Japanese Patent No. 4788577 discloses mounting a plurality of LEDs upon a long, thin printed wiring board in the longitudinal direction thereof, and illuminating an original by converging the light from the plurality of LEDs using a light guide.
However, the invention disclosed in Japanese Patent No. 4788577 does not disclose the manner in which the light guide is attached to a base member. Research performed by the inventors of the present application has shown that shininess, fogging, and so on occur in an image when the light guide expands due to heat. FIGS. 16A to 16D illustrate an example of fogging and shininess occurring when reading a spread thick original such as a book or the like. As shown in FIG. 16A, when a spread thick original P is placed upon a platen glass 140, the central area of the original is distanced from the platen glass 140. As shown in FIG. 16B, the reading result designed to be obtained is obtained in the case where the light guide is not warped. However, if the light guide is warped, there are cases where fogging will occur in the center of the image, as shown in FIG. 16C, or shininess will occur in the vicinity of the center of the image, as shown in FIG. 16D.